Brake Servo Weirdness!

[roundy]

So I am riding home the other night, very wet and the warning triangle comes on, brakes still working ok but when I pull into the drive the triangle starts flashing.

I turn her off and back on again and the brake light comes on permenantley and the servo runs. After a lot of fafffing about and changing the rear microswitch I come to the conclusion that the battery is shot as its dropping to like 5/8v when cranking - so I change it.

Then again, turn the ignition and the servo runs straight away and brake light on constantly. I then crank over the engine and the servo stops and the light goes out.

Took a ride (approx 40 miles) and then half way on my return the warning triangle is back on again, just getting toward the end of the ride and the flashing light starts and I loose servo, turn off, back on again and all ok.

When I finally arrive home I switch off, and then back on and the servo is running constantly again, but I also notice the brake light filament has gone so I replace. Still getting the servo running non-stop and brake light on when I turn on, but all goes off when I start her up.

Then a moment of madness and I decide to turn the ignition on with the front brake held in, of course the brake self check fails, so off again and release brake lever and back on - no servo and no light - all OK ???? Turn off and back on a few times, all ok

So this morning I go to the bike, servo and light on again when ignition switched on, do the same procedure as above and all ok?!?

W....T....F?!?!! I am so confused!!!

 

[Fanum]

Hand guards touching brake lever?

 

[roundy]

Sorry, should have said, it's an 1150R - no hand guards...

The switches are not stuck...

 

[Fanum]

I seem to remember a Steptoe post about the valves in the Servo getting gummy and sticking......he described how to clean them up (it's something that many people ditched the servo because of, where in fact it's a simple fix was the jist of it) ....not sure it would cause these symptoms, but do an advanced search using his name and servo etc and it may well pop up....if it's not in the Font Of All Wisdom section

 

[Fanum]

Not found the thread on the solution yet, but the problem is mentioned here on this thread (last post, from MickRW)

 

[roundy]

Yeah, I am having issues finding it too...found lots of similar posts...

I wonder if the fact the brake fluid is mega old (like 2yrs+) - the problem is this 1150R just sits in the garage and used when I have issues with my 1200RT (it's my dads bike but he doesn't use it)

 

[Fanum]

BINGO

 

[roundy]

Genius, thanks for that!

I really need to change the fluid out, which I'll have to do if I try this. I've read all the guides on how to do it but I have no idea how to get around the fact BMW don't sell the filling adapter anymore? What can I use to get a head of fluid....?

 

[NeilDD]

Hi Roundy,
Try using a small funnel or syringe to get your head of fluid.
Have a look on www.shawstainless.co.uk for the filling adapter. as I'm sure its the same as on the brake calipers etc.

HTH
Neil

 

[Steptoe]

but I have no idea how to get around the fact BMW don't sell the filling adapter anymore? What can I use to get a head of fluid....?

Don't read the american version of how to bleed the servo system. They love making a mountain out of a molehill....... .

You just pour the fluid in from a beaker. You don't need a "head" of fluid.

As the fluid level drops in the servo reservoirs, so you just pour new fluid in to keep the level from going too low.

If you can read without moving your lips and can control your saliva then you should be able to pour fluid from a beaker into the servo.

 

[The Grey One]

Don't read the american version of how to bleed the servo system. They love making a mountain out of a molehill....... .

You just pour the fluid in from a beaker. You don't need a "head" of fluid.

As the fluid level drops in the servo reservoirs, so you just pour new fluid in to keep the level from going too low.

If you can read without moving your lips and can control your saliva then you should be able to pour fluid from a beaker into the servo.

That's a big "if" for some

John

 

[DrFarkoff]

If you can read without moving your lips and can control your saliva then you should be able to pour fluid from a beaker into the servo.

I fear My Saliva mixing with my brake fluid So I made a wee funnel thing

Tis a less arduous task now but ya gotta get yer eye over the pipe and judge when to stop just at the top of the wee white filter thing for the correct level

 

[roundy]

Thanks for the pointers, feel a lot more comfortable having a go at this now! Need to do the RT as well (gearbox is still going well Steptoe, FD gone now!!)

The spacers for the calipers are a must I assume?

 

[roundy]

Does anyone have the measurements for the spacers in mm and not inches?

 

[Ian J Hartley]

I used the brake pad as a template, made them a bit smaller. Cut them out of some gash 5mm plywood. The object of the exercise is to push the pistons fully home so that:

A . You get rid of all the old fluid

B. The correct fluid level is set.

You could use the brake pads to do this and wedge between the pads with calipers unshipped, or between the pads and disc if calipers fitted. Find a method your comfortable with.

 

[roundy]

Thanks for that - good idea!

 

[roundy]

Is the rest of the US guide good to follow? Or is there a much simpler way of changing the fluid...?

(Just read through it and it does look wordy!)

 

[DrFarkoff]

It's like this

Handlebar master cylinder to ABS unit there are 3 nipples that you open in sequence a, b c and then a again

The footbrake is done the same way but the other three nipples are opened in sequence x y a and then x again

this is a BMW official procedure not the Merkins

To get more room you can remove the main ABS plug as this is all hand foot powered stuff BUT cover the socket with a sandwich bag or something to prevent any fluid dropping in there eh?)

Once you have done this bit and topped the levels in your master cylinders and refitted the horrible little rubber doofers and refitted your ABS connection you then flush any excess fluid away with copious amounts of FRESH water

Open the reservoirs on the unit and then start bleeding to the front and rear callipers

VR beside the reservoir = Vorderrad front wheel Usually larger than the rear one (Except for Mk1 versions where they were the same size)

and HR - Hinterrad rear wheel

NOTE BENE!!!! Even tho the brakes may be Linked Be Warned

Reservoir for Front is FRONT ONLY

Reservoir for Rear is REAR only

Don't try flushing the rear system while topping up the front you will fuck the servo! As a poor fellow did with an RT he came asking about!

Roundy If it still pisses about get it out and removed or fit a new unit (unless you know the replacement unit history) I consider these bastard systems dangerous There's no other braking system out there that has scared me so much in so many ways!

Between Servo being full power @ 20 mph and no Anti lock operating doing 60 mph and No servo only residual braking (re residual braking Yes some work and some don;t and I don;t know why they do or don;t? but of the 2 that were dodgy that I encountered you would be better pishing straight at a hurricane force wind than try to stop a K1200LT with what was left!)

I've had about 6 horrible fecking episodes on them and decided that whipping them off or a Brand new system was the only way to go

 

[roundy]

Thanks for the steps...are the nipples labelled???

Also, just to double check I am just using the foot and hand brake pressure to bleed and not the servo power itself?

 

[DrFarkoff]

Thanks for the steps...are the nipples labelled???

Also, just to double check I am just using the foot and hand brake pressure to bleed and not the servo power itself?

Heres a link http://advwisdom.hogranch.com/Wisdom/service_abs3.pdf look for control circuit bleeding

Servo ABS has 4 circuits all of which are independent!

Front Control circuit = Handlebar to ABS Block

Rear Control Circuit = Footbrake to ABS Block

Front Wheel Circuit = ABS Block to Front Wheel callipers

Rear Wheel Circuit -ABS Block to Rear Calliper


Only wheel circuits are flushed using funnel and servo

Control circuits are done by hand and foot and via the nipples on the ABS Block